1. Field of the Invention
This invention relates generally to the pressing and alignment of radially-oriented toroidal magnets and more specifically to a method and apparatus for pressing and aligning magnetic powders into a radially-oriented unitary toroidal shape.
2. Description of the Prior Art
Radially-oriented toroidal magnets are well known in the permanent magnet art. Their use has been limited, however, because of the difficulties encountered in fabricating them and because they lacked the ability to provide sufficiently high magnetic coercivities and remanences for certain applications. Radially-oriented toroidal magnets are usually fabricated by joining discrete annular sections which are individually magnetized in a straight rather than in a radial magnetic field. The annular sections are then bonded together to form a toroidally-shaped magnet. However, because of the straight magnetic field employed during manufacture the radial field of the magnet is not a true radially-aligned field, but a synthesized radial magnetic field. For some applications this is satisfactory but for other applications the synthesized field does not produce the desired high magnetic field strength because of the non-radial alignment of the field.
In applications involving relatively small radially-oriented toroidal permanent magnets the bonding of sections to form a toroid is not practical due to their small size. There exists no known method or apparatus for the pressing and aligning of small unitary toroidally-shaped pressed magnetic material.
An example where small, radially-oriented toroidal permanent magnets are needed is in millimeter-wave applications, such as travelling wave tubes, particle accelerators, and travelling wave tube amplifiers, for example. The need for improving the magnetic intensity per unit weight of such magnets to thereby improve the overall size and cost of the magnet has long been recognized.